First make the crust. Sift the flour and baking powder onto parchment paper. In a bowl of a stand mixer fitted with the paddle attachment, combine the oil, sugar and vanilla, and blend at medium speed. One at a time, add the eggs, incorporating the first before the adding the second, and blend. Add the orange juice, if using and blend. Reduce the speed and add the flour mixture, gradually to make a dough.

Divide the dough into 2 parts and flatten each to make a disk. Wrap each disc in plastic wrap, stack the discs on a plate, and refrigerate until the stiff enough to work easily, at least 2 hours.

Meanwhile make the filling(s). For the poppy, raspberry-and/or apricot fillings, combine the ingredients in small bowls, stir to blend, and refrigerate for 1 hour. For the chocolate combine the ingredients in a small bowl. Transfer half the filling to the centerof an 18 inch piece of plastic wrap, fold the wrap over the filling to enclose it, and squeeze the mixture to create a log 1-inch in diameter. Repeat with the remaining filling and freeze the logs.

Preheat the oven to 350 F. Flour a work surface well and roll 1 of the discs out on it. Using a 3-inch glass or round cookie cutter, cut out rounds. Pipe about 1 tablespoon of the poppy seed, raspberry and/or apricot filling(s) in the center of each round, wet the edges with water and bring up the dough together to seal. Alternatively, drop the filling onto the dough by heaping tablespoons. For the chocolate filling, cut the frozen logs onto 1/2 inch discs. Fill the rounds by placing a disc in the center of each form and seal.

Transfer the hamentashen to 1 or more cookie sheets and bake, in batches if necessary, until pale gold 12 or 14 minutes. Transfer to a rack and cool.